<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>08_相对定位</title>
        <style>
            .fu{
                background-color: #ff0;
            }
            .fu>div {
                width:100px;
                height:100px;
            }
            .z1 {
                background-color: #f00;
            }
            .z2 {
                background-color: #0f0;
                /*固定定位：会脱离文档流 释放布局空间*/
                /*移动参照物：html根元素*/
                position:fixed;
                top:0;
                left:0;
            }
            .z3 {
                background-color: #00f;
            }
        </style>
    </head>
    <body>
    <div class="fu">
        <div class="z1">红</div>
        <div class="z2">绿</div>
        <div class="z3">蓝</div>
    </div>

    </body>
</html>